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GARY F

castle nuts with cotter pins

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I just removed all my pistons from my straight eight flat head 37 Olds. Each connecting rod cap has castle  nuts with cotter pins. When I replace the pistons and use the castle nuts and torque to specs I am sure half of the nuts wont line up with the pin hole.  What do I do , crank them down more or can I get new nuts with the plastic in them  I call locking nuts so they do not back off after torque. Thanks for replies.

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Back then, they didn’t use torque wrenches. They just tightened till they were satisfied and lined up the hole for cotter pin. I think the lock nuts that don’t have the plastic ring would be better. Mike

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3 minutes ago, Mike "Hubbie" Stearns said:

Back then, they didn’t use torque wrenches. They just tightened till they were satisfied and lined up the hole for cotter pin. I think the lock nuts that don’t have the plastic ring would be better. Mike

Well, sort of.  Torque wrenches became common tools for the automobile in the 1940's, and there are specifications for such things as head torques back into the mid 1930's.  Chrysler was one of the first users of torque wrenches on an assembly line, and that usage seems to go back into the 1920's.

 

I would agree that a lot of backyard mechanics were versed enough that they'd just tighten until it "felt right".   

 

On a previous comment on a previous thread about this topic, someone said the instruction should read something like "tighten until the bolt breaks of the threads strip, then back off a quarter turn".....

 

My friend The Wizard mechanic says that all you need to do is torque rod cap bolts to about 40 pounds-foot, no pin needed, and he works on Porsche race engines.  I'm doing my Packard engine now, plan to torque to 35 or so and then see where the hole in the bolt is, and wing it from there....

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A long time Packard mechanic told me if the hole does not line up they were supposed to take the not off and file it down a bit then retry and repeat as necessary.  Since then I have always done it that way, even on my lowly Pontiac.  After about three nuts you do not even need two tries.  Surprisingly usually about five of the twelve nuts did not need filing in the three times I had my engine apart.

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Just to add to what Tinindian outlines some castellated nuts (mainly big end and main bearing) I have found to be hardened and to remove the small amount of material I have had to use the side of a grind stone to give it a gentle rub.  Main thing is not to take too much off and keep it square.

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Sometimes the start of the threads and the location of the slots on old castellated nuts are not always machined oriented the same to each other. so, just swapping the positions of the nuts gets them to line up with a cotter hole at very near to all the same torque without need of filing/grinding.

 

Paul 

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I always notch the end of the bolt with a small file to indicate where the cotter pin hole is,

and after reaching the proper torque spec, either advancing the nut to the next slot or backing it off, which ever is closer.

Taught that back in '63 working on the assembly line at J.I. Case Co. combine plant in Bettendorf, Iowa

 

Mike in Colorado

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My 23 Moon has lock wire.  I used to design jet engines for GE and we lock wired every thing.  If it is good enough for a military jet engine it is good enough for my slow rotating car engines.

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Hand filing the nut likely results in poor contact between the nut and rod. Lots of ways to skin this cat. Likely makes little difference what ever method you choose. The PAL nut atop a standard rod nut seems best to me.............Bob

Edited by Bhigdog (see edit history)

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If you use a castle nut and wire or cotter pin, the nut will never come off.  Not true with the prevailing torque or nylock nuts.  Maybe they will be OK, but why take a chance.  

 

I too was schooled to move the nut to the closest location for the hole in the rod bolt. + or -.

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8 hours ago, jan arnett (2) said:

My 23 Moon has lock wire.  I used to design jet engines for GE and we lock wired every thing.  If it is good enough for a military jet engine it is good enough for my slow rotating car engines.

Last time I toured the GE Evendale plant, there were 2 guys in the assembly department having a "hardware" fight, throwing lock washers at each other.

 

Plant manager was not happy............

 

Mike in Colorado

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Double nutting or jam/pal nuts are not new, neither are nuts that bind, like Nylocs do. There were early versions of nuts with the last threads to engage  made to bind, but they were not used in engine bottom ends.

 

However, there's  very good reason that connecting rod and main bearing cap nuts used castillated nuts and safety wire or cotter pin for many decades when other type jam fasteners were available and less labor intensive in a production line.  Castillated nuts won't even come loose with the extreme temperature change expansion/contraction, and shock load forces that those nuts have to deal with.

 

I've seen instance where Nyloc nuts came loose, that someone had used on an engine cooling fan,  because the nylon inserts popped out. Not only are they not period correct they are not good for many auto engine applications, or you'd see them used more by the auto industry. 

 

Paul

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Out of curiosity, has anyone ever had a properly tightened rod nut (not cottered or wired) come off?

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17 hours ago, DonMicheletti said:

Out of curiosity, has anyone ever had a properly tightened rod nut (not cottered or wired) come off?

 

No.

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17 hours ago, DonMicheletti said:

Out of curiosity, has anyone ever had a properly tightened rod nut (not cottered or wired) come off?

Not on any engines I ever worked on in 50 years. All had the manufacture's type of main and rod bearing fasteners and I didn't see any  good reason to change to something else.

 

I have seen bolt-on cylinder jugs cracked because the owner used hardware store nuts and lock washers instead of the original special shaped double nuts designed to hold when lock washers will not in that application. That cost the owner a few thousand dollars for thinking modern fastener methods are always better than what the original designers had figured out long ago.  

 

Paul

Edited by PFitz (see edit history)

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Quote

 

Thanks for all the replies. I will put it back the way it came off. Cotter pins.

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I would tighten until the nut slot lined up.  A rod bolt is not a good place for an insufficiently tightened nut. Torque readings can be highly variable due to differences in friction between the nut and cap.  I suspect sanding/filing or grinding the nut would only make this condition worse.  I've seen on some (newer) engines the final bolt tightening is specified by angle of turn rather than torque.  I suspect it gives more consistent tension in the bolt.

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Always tighter to get the pin in, not looser. Well... unless its a wheel bearing, but that is a whole different game.

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A lot of torque specs show a range like 40-45. Torque to the lower spec and then tighten if needed to allow the lock wire/carter pin to be installed. I also agree never loosen always tighten to fit. Once a bearing cap, rod or main, is tightened the bearing can be very slightly deformed. In this case loosening the nut/bolt can allow the bearing shell to move slightly. I do not know if this is an issue, but it just seems wrong. Slightly tighter aligns the lock hole and does not allow for bearing movement. Just my $.02 and maybe not worth that :P.

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8 hours ago, MikeC5 said:

I would tighten until the nut slot lined up.  A rod bolt is not a good place for an insufficiently tightened nut. Torque readings can be highly variable due to differences in friction between the nut and cap.  I suspect sanding/filing or grinding the nut would only make this condition worse.  I've seen on some (newer) engines the final bolt tightening is specified by angle of turn rather than torque.  I suspect it gives more consistent tension in the bolt.

 

This post made me want to add to my earlier post....

 

Like @MikeC5 said, there are other variables in torque values.  Torque on a nut or bolt is really a way to set constant clamping pressure on an assembly. To get a repeatable clamping pressure you need equil torque pressure from the fasteners. The only way to do this is to have known and repeatable values for all variables that effect clamping pressure. With this in mind, all nuts, bolts, studs and threaded holes should be clean and lightly lubricated. The fasteners should be free of any resistance to tightening. IE, be able to finger tighten until the nut/bolt contacts the part to be clamped. The surface that the bolt/nut contacts must also be clean and lightly lubricated so friction is at a minimum. With this in mind, any friction locking method, Nylock or interference thread or similar will cause false torque and therefore improper clamping forces if torque is the method used. In the rare event a locking fastener is used in a torque tightening method it is absolutely mandatory to use NEW factory fasteners. This is the only way to have a known variable resistance to start with because once used the interference is less than it was when new.

Torque is just a measurement of friction and resistance. This is why everything must be smooth and fresh and clean to allow consistency.

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Actually, back in the 30’s, you used stretch and measured the bolt before and after tightening it down. It is the PROPER way to do rod bolts............only problem is finding the figures. Have I ever seen a rod bolt or nut fail? Yes, common on the early rods that used a hinged rod like Cadillac. I have had engines suffer rod bolt failure..........yes.........from the 50’s to modern engines of today, but ALL were under extreme use........ie ...............drag racing.

Edited by edinmass (see edit history)
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PS - When  Possible, use modern rod bolts and nuts.........but it can be expensive and require machine work to the rods. I would not use modern nuts on old bolts, use the castle nuts and tighten them till they align. For many years, torque wrenches were often not calibrated accurately, and thus they were not reliable. The stretch method was and is accurate with NEW bolts and nuts. 

Edited by edinmass (see edit history)

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When I did them in my Cadillac I just did them up until tight and then either nudged them slightly forward or back to get it to line up with a hole

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Very interesting topic.  In relation to  split pins and castle nut hole alignment. I often use loctite in conjunction with the split pin. It is extra insurance. I always gently wind the nut back so the pin is not loose . This  stops the pin vibrating. Well designed set ups have the bolt cross drilled as well.. ..As to the importance of torque settings..  The alloy conrods used in some engines stipulate very emphatically not to over tighten the bolts. Use only a spanner 6” long so as not to apply too much torque. (Stutz). Over tightening would distort the conrod and is /was the most common cause of rod failure.  Ditto for BSA motorcycles as well. Good for up 6000 rpm. 

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